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February 21, 2005

Titan Rising, Part I

by Sam Savage

Just over a month ago, the European Space Agency's Huygens probe descended through the atmosphere of Saturn's giant moon Titan. The probe sent back stunning close-up images of a world never before seen is such detail In this, the first of a two-part series, science reporter Michael Benson shares his impressions of the event from his front-row seat at ESA's control center in Darmstadt, Germany.

Astrobiology Magazine -- It's not very frequently, in the early 21st century, that one can observe grown men cry for reasons other than disaster. We've seen plenty of it due to tragedy, of course: the recent tsunami; the hell of Iraq; massacres in Darfur; Israel vs. Palestine. The list is practically endless. But tears of joy? They're practically unheard of.

There are exceptions, however. Take the successful arrival, on distant, ringed Saturn's mysterious planet-sized moon Titan, of robot Huygens, Europe's first mission to the outer solar system.

Orange-brown Titan is larger than Mercury and Pluto and is shrouded entirely by a dense, opaque, frigid atmosphere. Those gasses include complex molecular hydrocarbon chains believed to be the building blocks of life. With a surface only glimpsed indistinctly through the petrochemical smog - and then only in the last year or so, by Huygens's "mothership," NASA's Cassini spacecraft - and with some theories holding that the place must have lakes or even seas of liquid ethane and methane, Titan is one of the most mysterious spheres within the range of robots from Earth.

Still, that's 3.5 billion kilometers away. Given the distances and uncertainties involved, the Huygens mission is one of the most audacious forays into deep space ever attempted by human beings. It's also the first time that a landing has ever been attempted on a moon other than the Earth's own.

It was Friday morning, January 14th, in Central Europe. After 20 years of development and more than six years of flight, Huygens was finally scheduled to plunge into Titan's hydrogen-methane atmosphere - hopefully revealing some of the secrets of the place along the way.

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The European Space Agency's control center in Darmstadt, Germany, is a pretty high-tech affair. Rows of large computer screens, banks of telephones, winking lights, and large projector screens with images of Saturn and the Earth provide all the various Star Trek touches one might expect from such a facility.

No expense has been spared, and with good reason: apart from Huygens, this is the place where an ESA spacecraft orbiting Mars is currently being controlled, as well as a second robot now on its way to visit a comet; another European mission has just settled into orbit of the moon, and a fourth is monitoring the Earth's atmosphere. It would be no exaggeration to say that Europe is currently enjoying the first flushes of a real space exploration renaissance.

But no Euro-mission can boast anything like the longevity or ambition of Huygens. The 3.3 billion dollar joint NASA-ESA Cassini-Huygens project was first conceived in 1981, when a European proposal to collaborate with NASA in sending a probe to Titan was augmented by the American idea of equipping such a mission with a far larger Saturn orbiter.

The design called for the Huygens probe to be mounted on the side of Cassini; it would effectively hitch a ride to Saturn on the orbiter. The construction of the two probes was already well underway when money troubles arose on the American side. In 1994, then-NASA administrator Dan Goldin directed his agency to focus on "cheaper, faster, better" robotic explorations. The directive threatened to cancel Cassini altogether, and thus Huygens.

As befits a mission originally conceived there, it was the Europeans who ultimately saved the day. In June of that year the director of the European Space Agency sent a sharply worded letter to US Vice President Al Gore. "Europe "¦ views any prospect of a unilateral withdrawal from the cooperation on the part of the United States as totally unacceptable," the letter read in part. "Such an action would call into question the reliability of the US as a partner in any future major scientific and technological cooperation." Cassini-Huygens was restored, though the Cassini part of the program had its budget severely cut, reducing many of its capabilities.

Still, NASA's school-bus-sized Saturn orbiter is by far the largest robot ever sent to the outer solar system. It was named after the French-Italian astronomer Jean-Dominique Cassini, who in 1676 discovered the large gap in Saturn's rings which now bears his name. The namesake of ESA's atmospheric probe is Dutch astronomer and scientist Christiaan Huygens, who discovered Titan in 1655. Huygens also was the first to realize that Saturn's mysteriously symmetrical appendages - protrusions extending out from the sides of the planet, which had been observed, but not understood, by a baffled Galileo in 1610 - were in fact "a thin flat ring, nowhere touching."

Saturn has lent its shape to many a science fiction scenario. It is without a doubt the most futuristic-looking planet, and as with its larger "gas giant" cousin Jupiter, Saturn's free-wheeling squadron of moons are a kind of miniature solar system. Titan, however, is a real stand-out: the only moon known to possess a substantial atmosphere. As a result, the Huygens probe needed an archetypically flying-saucer-shaped heat-shield for the first part of its entry into the Titanian atmosphere.

When I mentioned Huygens' shape to science-fiction author and futurist Arthur C. Clarke a few years ago, he chewed the information over for a minute then quipped: "Maybe that's what they are."

Meanwhile Huygens' top managers - the scientists and engineers that have been shepherding this mission to completion, some of them for more than two decades - were absent from that auditorium. That's because they were in that gleaming control center, which is in another building. On a big screen in the media room, we of the press could occasionally see them as they were interviewed from a safe distance by ESA's PR woman.

Mysteriously, the televised slice of control room visible to us behind the top Huygens brass - which included Jean-Pierre Lebreton, the mission's manager; Claudio Solazzo, its operations manager; and several of the "P.I.'s," or Principal Investigators, meaning the scientists in charge of Huygens' six instruments - was almost entirely empty of activity.

We saw, in fact, a row of blank screens and vacant chairs. For some reason, the camera angle chosen to transmit the excitement of Huygens' arrival to the media showed a main ESA control room seemingly ready for the char-force, or maybe a late-night fuse-changer. This empty shell is the facility geared up to monitor the success or failure of an epochal landing on Saturn's moon? How can it be?

As the minutes ticked past 11 AM on January14th, the answer would have been obvious to anybody with a pass granting access. The mass of anxious Huygens scientists and engineers were huddled, not around a chair at one of the shiny new consoles, or in front of a nice poster-sized graphic rendition of the Huygens trajectory as it lands on orange Titan, or what have you. No - they were gathered around a small, school-sized desk in the back of the room.

That desk had at its center not some high-tech communications device, but an extremely modest black plastic Dell laptop. A computer of the kind used by students who do mostly word processing, sitting on the kind of banged-up desk that is generally shoved into the back of an office near the rest-rooms to put the coffee machine on.

This whole bizarre scene, in which all the fancy machines of Europe's expensively high-tech Mission Control were abandoned in favor of an old plastic laptop, had a distinctly improvisational flavor to it. And the reason we didn't see it on-screen in the media room is that ESA's PR professionals had evidently decided, probably correctly, not to puncture the glittering, everything-under-control mythology of robotic spaceflight.

We therefore were looking in the opposite direction from that hastily cabled-together, back-of-the-room rig where the real action was. But even the most cursory student of space-flight history - of the shaky last years of the MIR space station, for example; or of the gaffer-tape and cardboard that saved Apollo 13 in 1970, after their service module suffered an explosion on the way to the moon - will recognize and appreciate the texture and tone of this last-minute ESA control-room solution. It had the true flavor of space exploration, not its mass media representation. It revealed it as what it truly is: a highly complex activity subject to rapid-fire improvisation and technical smarts.

And so the Huygens chiefs intently watched the screen of that Dell, which was hooked up to the Internet; a small webcam window was open. With the blurry, pixilated vision characteristic of all webcams, ESA's humble laptop revealed another control center. This one was on the other side of the planet, and running the massive Greenbank Radio Telescope in West Virginia, USA.

In the pre-dawn darkness of the eastern half of North America, the world's largest fully steerable radio telescope happened to be in a perfect Earthly longitude for listening to Saturn. And so all 110 square meters of the Greenbank dish's steerable surface was tilted towards the ringed planet - more specifically, towards Titan.

Although the laptop-and-webcam link between these two control centers might seem almost bizarrely low-budget, a plastic paperclip holding together two lengths of golden chain, the two facilities so linked are among the most advanced of their kind on the planet. The setup, Huygens mission manager Lebreton later explained to me, was in fact what it looks like: a last-minute fix.

It was the result of realizing, quite late in the game, that the only way for the Huygens team to verify that the incoming signal actually was from their probe (assuming they received a signal at all; one planetary scientist had estimated the chances of Huygen's success to me as "about fifty-fifty") was if they could actually see the shape of the wave-form as soon as it was available. And the fastest way to do that, it turned out, is via web-cam link from Greenbank.

And so the clock ticked in Darmstadt.

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Listen to sounds from the microphone onboard the Huygens during its descent (wav file format, approx. 600 kB each):